Considering The Rotational Centrifugal Force In The Study Of The Lunar Thermal Evolution

The study on the lunar thermal evolution,it can increase the understanding of the lunar formation process and the subsequent evolution trend,and even help to explore the lunar origin.For the study of the influence of centrifugal force on the lunar thermal evolution,the size and composition of the lunar core are not very clear.Therefore,the solution is the temperature field of the lunar mantle region,we need to refer to the size of the lunar core,so this paper has done two aspects of study.(1)We estimate the size and density of the lunar core.They can be estimated according to the second degree of gravity field model and selenophysical libration parameters from LLR(Lunar Laser Ranging).We used the high resolution lunar gravity field model GL1500E to evaluate the lunar core's size and its density,which are inversed through a nonlinear particle swarm optimization.A large number of inversion counted that the outer radius of the outer core is about 469 km with a corresponding density of 4613 kg?m^-3,the radius of inner core is around 303 km with a corresponding density of 7004kg?m^-3and the density of mantle surrounds 3340 kg?m^-3.It is quite close to the geological value of 3360 kg?m^-3.The radii of inner core and outer core are quite close to other recent studies as well.The size and density of lunar core found here can be therefore meaningful.If the lunar core is composed of pure iron and ferrous sulfide,our study shows that the inner core is mainly composed of pure iron whereas the outer core is largely composed of ferrous sulfide.(2)According to the governing equations of thermal evolution,we deduced the dimensionless version for the governing equations.Their weak forms of finite element method were also derived in the two-dimensional rectangular coordinate system,Referencing obtain the outer core radius of the moon,the study area is determined.Considering the angular momentum of the Earth-Moon system is nearly conserved,we estimated the lunar rotational angular velocity after its formation.Then the rotational centrifugal force was considered in the governing equations.Results indicate that the rotational centrifugal force promotes to generate high temperature convection columns perpendicular to the rotation-axis,but producing low temperature convection columns along the rotation-axis.Compared with the case of rotational centrifugal force non-considered,it is found that the rotational centrifugal force has a cooling effect on the lunar mantle,and the greater the centrifugal force,the more obvious the effect.This mechanism needs to be considered in the lunar thermal evolution.